Cancer risks of hookah (shisha, narghile) tobacco use require further independent sound studies

Abstract

In the Letter on the risk for pancreatic cancer associated with the use of water pipes [type of device and use (tobacco, molasses-tobacco, etc.) however not specified], Fouad et al. regret that there would be a dearth of published studies on the health effects of this form of smoking.1 This is not exact as, for instance, a recent work from Turkey has recalled important pioneering works on hookah smoking carried out in the 1980s and 1970s by independent researchers.2 Contrary to a common misperception (influenced by the popular press too often interested in “fresh” scientific publications only), biomedical research on the multi century-old hookah has not begun at the dawn of the 21st century (year 2002).3 Dozens of valuable and relevant studies have remained for too long under the dust of shelves in medical libraries. Although the question here is not that of the quantity but rather that of the quality of the work, it is noteworthy that an impressive number of articles have been published on this issue since highly funded research centres dedicated to the fight of this form of smoking were set up 7 years ago. A neologism (“waterpipe” in one word) has even been created for this purpose.4 Three references are cited by Fouad et al. to support the important claim that “the longer duration of a Water Pipe Smoking session leads to a much higher yield of tar, nicotine, carbon monoxide, polycyclic aromatic hydrocarbons, and heavy metals than cigarette smoking. The water pipe smoker may therefore inhale the equivalent of 100 or more cigarettes”.1 However, one of these references (Chaouachi, Int J Environ Res Public Health 2009) is actually a critique of this statement and shows that the levels and number of toxic substances in cigarette and hookah smoke are completely different from each other. What is unfortunately not discussed is the fact that the elevated yields of toxic chemicals, as reflected in the other cited paper (Shihadeh and Saleh, Food Chem Toxicol 2005), were generated through the use of an unrealistic narghile smoking machine drawing one puff every 17 sec for a full hour with the charcoal in the same position. Such a set-up is supposed to mimic the “average” narghile smoker. Yet, while “averaging” a complex human behaviour (i.e. reducing its wide variations to periodic puffs drawn every 17 sec) over a short span of time (5 min, for instance) would be mathematically and epistemologically acceptable, extending this process to 60 min, as if a narghile smoker were a robot, represents a gross methodological error.4, 5 Furthermore, it should be noted that not only all these chemicals are not mutagenic but also no details are given about their biokinetics, i.e. how they do reach and enter the pancreas. Consequently, rapid equivalences implying an identical chemical composition of two different smokes are scientifically unacceptable. This applies not only to mainstream smoke (the one inhaled by the smoker) but also to side-stream smoke (strikingly visible with cigarettes although almost inexistent with hookahs).5 In a recent article based on the above-mentioned controversial smoking machine, a tunnel was used to collect side-stream carcinogenic emissions that were measured only 1 min after the quick-lighting charcoal was lit and put atop the bowl of the pipe.6 Among other biases (ageing and dilution processes, ventilation holes of the cigarette not blocked), the tunnel was disproportionate in size given the obvious spatial differences between a thin 10 cm long cigarette and a portly 50 or 60 cm high hookah. Then, in the real world, users always wait up for several minutes before setting about smoking. During this time, highly toxic particles, appearing as a visible black plume of smoke at first, are emitted from the (non-natural) charcoal.4, 6 From Roffo's pioneering interest in narghile smoking 70 years back to that of El-Aasar and his colleagues 3 decades ago, and leaving aside other independent researchers, particularly in Asi